Merck Blood Thinner Study Ends in Stroke Patients, Limiting Possible Sales

A study of Merck & Co.’s vorapaxar, an anticlotting pill that had potential for $5 billion in annual sales, was halted and a second trial narrowed in scope, limiting the drug’s possible use.

All participants will stop taking the drug in the trial of 13,000 patients who began the medicine at the time of a heart attack or chest pain, researchers at Brigham & Women’s Hospital in Boston and the Duke Clinical Research Institute in Durham, North Carolina, said today. A second study, of 26,500 patients with prior heart problems, will be stopped for the 25 percent who had suffered a stroke.

Shares of Whitehouse Station, New Jersey-based Merck declined the most since April 2009. Vorapaxar was touted by the company as its most promising experimental drug from the $49 billion purchase of Schering-Plough in November 2009. The company doesn’t know if it will be able to file for approval on the basis of a remaining study, for long-term clot prevention, said Peter Kim, president of Merck Research Laboratories.

“While the press release does not clearly say this, it appears that excessive bleeding may have been the culprit,” wrote Tim Anderson, an analyst at Sanford C. Bernstein & Co. in New York, in a note to investors titled “Vorapaxar (aka TRA) Bites the Dust.”

While the loss of the pill once known as TRA won’t “substantially” hurt Merck’s financial results, “it does strip away the company’s highest profile pipeline drug,” he wrote.

Results Unknown

The research was halted by an overview board charged with protecting patient safety in both trials, the institutes said. Even the researchers conducting the study haven’t been told why it was halted to ensure a fair analysis of the data, said Robert Harrington, study chair and director of Duke’s Clinical Research Institute, in an e-mail.

The halted trial, known as Tracer, had a greater proportion of patients who were taking aspirin and New York-based Bristol- Myers Squibb Co.’s Plavix in addition to vorapaxar, Harrington said. Plavix and aspirin have been shown to increase the risk of bleeding.

“That might be important,” he said. “We just don’t know yet.”

Merck will review the results from the halted study once the analysis by the Duke researchers is complete, Kim said in a conference call with investors. The company also will evaluate whether changes need to be made to the remaining trial, now that its sample size is smaller.

Merck declined $2.46, or 6.6 percent, to $34.69 at 4 p.m. in New York Stock Exchange composite trading of 74 million shares, more than five times the three-month daily average. The company was the biggest decliner on the Standard & Poor’s 500 Index. Merck has fallen 11 percent in 12 months.

‘Little Value’

“Following today’s selloff, we believe Merck shares reflect little value for TRA,” said Chris Schott, an analyst at JPMorgan Chase & Co. in New York, in note to clients. He maintained his recommendation to buy the stock.

Schott said the possibility that the remaining trial would lead vorapaxar to become a broadly used drug for preventing secondary heart conditions is “off the table, at least for now.”

A Citigroup Inc. analyst, John Boris, reduced his rating on Merck to “hold” from “buy” and cut his price target to $39 from $45.

Vorapaxar might have generated peak sales of $5 billion or more a year if the treatment were proven safe and effective, said Robert Hazlett, an analyst at BMO Capital Markets in New York. The drug is still in development for patients with a previous heart attack or with blood clots deep in the legs, known as peripheral artery disease.

The drugmaker previously said it planned to file for U.S. regulatory approval of vorapaxar this year. The drug, intended to prevent cardiac complications and deaths, was one of four cardiovascular treatments Merck has in final testing each with the potential for at least $1 billion in annual sales by 2016, according to BMO’s Hazlett.

To contact the reporters on this story: Michelle Fay Cortez in Minneapolis at mcortez@bloomberg.net; Tom Randall in New York at trandall6@bloomberg.net.

To contact the editor responsible for this story: Reg Gale at rgale5@bloomberg.net

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